This invention relates to a grain drying system and method for drying grain around the interior of a grain bin wall while minimizing air and heat loss above the level of grain stored in the bin.
When grain is harvested, it has a percentage by weight of water making up its composition. In order to bring the moisture content of grain to a safe, storable level to prevent spoilage, grain drying is commonly used. If the amount of moisture is too high, mold can form and the grain will break down and possibly promote insect infestation. Therefore, a drying bin enclosed by walls and roof is used to dry the grain. In the typical grain bin drying installation, heated dry air is forced upwardly from a plenum chamber through an air permeable subfloor upon which the grain is supported. A fan and air heater assembly located outside of the grain bin blows heated air into the plenum chamber below the air permeable subfloor. The heated, dry air removes moisture from the grain and continues upwardly to the bin roof where it escapes to the atmosphere through vents in the bin roof. In order to assure grain quality stored for extended periods, it is necessary to maintain a predetermined moisture content of the grain by using maintenance levels of heated dry air in the grain bin, as will be apparent.
Although the aforementioned grain drying system works quite well, where colder climates are encountered, spoilage can occur in grain located near the bin wall, due to condensation forming on the side wall when the outside temperature drops. In addition, grain is sometimes more densely compacted along the interior of the bin wall. To overcome the problem of grain spoilage along the interior of the bin wall, a variety of solutions have been offered. One type of equipment, as shown in U.S. Pat. Nos. 3,531,874 and 4,009,520, employs a plurality of perforated, vertical tubes which are mounted on the interior of the bin wall and communicate with a dry air source for introducing dry air into the grain bin along the interior of the bin wall. Another type of equipment uses perforated corrugated sheets mounted to the bin wall which also communicate with a dry air source to introduce dry air into the grain adjacent to the grain bin interior wall.
While the problem of grain spoilage along the interior of the grain bin wall has been substantially alleviated with such aforementioned equipment, they have nonetheless created a problem of wasted air and heat loss when the grain bin is not full. For example, if the perforated tubes or sheets (i.e., air passageways) extend to a height of 10 feet above the bin subfloor and the grain level is only 5 feet above the subfloor, most of the heated dry air passing through such perforated tubes (or sheets) escapes from the tubes above the grain level to escape through the vents the bin roof, without coming into contact with any of the grain along the grain bin wall. Using information for resistance of grains and seeds to air flow, with information concerning air flow in passageways at various pressures, it is estimated that a typical grain bin equipped with prior art bin wall air ducting systems may be losing in excess of 20 percent of total air and heat introduced into the plenum chamber under extreme conditions. The opportunity for substantial cost savings, while utilizing wasted heat and air, would be available with an equipment system and method which avoids the aforementioned deficiencies of currently available prior art equipment.